A portable telephone or cellular phone will be described below as an example of portable terminal device. FIG. 4 is a perspective view showing the appearance of a conventional cellular phone, and FIG. 5 is a block diagram of the interior thereof. The phone has a cabinet 1 comprising two cabinet half segments 10, 10a which are connected together by a hinge 11. The cabinet half segment 10 is provided with an antenna 6, microphone for capturing voice and a plurality of manual buttons 20, 20. The other cabinet half segment 10a is provided with a display 5 which is an LCD and a speaker 90 for reproducing the voice of the other party.
With reference to FIG. 5, a signal from a base station 7 is received by a receiver 61 via the antenna 6 and a duplexer 60 and sent to a control circuit 3 having a timer function. The duplexer 60 is a device which uses the same antenna for two-way transmission and which handles transmitted signals and received signals using the single antenna 6.
The control circuit 3 has connected thereto an incoming call alarm 50 comprising a ringer and vibrator for notifying the user of incoming calls, a memory 4 having stored therein an operating program, melody to be produced upon receiving an incoming call, etc., the display 5 which is an LCD for showing the state of communication, a manipulator 2 including the manual buttons 20, 20, the microphone 9 and the speaker 90.
The incoming call alarm 50 notifies the user of an incoming call received. The voice of the other party is emitted by the speaker 90, while the voice of the user is captured by the microphone and sent from a transmitter 62 to the antenna 6 via the duplexer 60. At this time, the display 5 shows the state of communication, etc.
Cellular phones have been proposed in recent years which are adapted to determine the location of the phone itself using GPS, i.e., Global Positioning System (see, for example, the publications of JP-A No. 2000-241964 and JP-A No. 1999-64482). The principle of GPS will be described briefly with reference to FIG. 6.
As shown in FIG. 6, the GPS antenna 8 of a cellular phone receives signals, termed C/A cord, from four artificial satellites V1, V2, V3, V4 whose positions are known relative to the earth. The C/A cord is transmitted also from the cellular phone. The time difference between the C/A cord transmitted from the phone and the C/A cord received from each artificial satellite is measured, and the measurement is multiplied by the velocity of propagation of radio waves to obtain the distance from the satellite to the GPS antenna 8. The position and height of the GPS antenna 8 can be determined by solving an equation representing a sphere (because the earth is a sphere) using the positions of the satellites and the distances from the satellites to the GPS antenna 8.
However, the cellular phone described has the following problems.
With an increase in the number of subscribers of cellular phones, problems arise as to how to use the phone in public places.
Cellular phones should not be used, for example, in hospitals since the radio waves of cellular phones are likely to cause a malfunction of medical electronic devices. Incoming call sound alarms cause a public nuisance if released in libraries or museums which must be kept quiet. In such cases, forcible restrictions on the use of cellular phones are desirable, but the matter is presently left to the discretion of the user. Especially as to incoming calls, if the subscriber is at a location accessible by incoming radio waves, it is impossible to shut off the incoming call unless the subscriber turns off the power source. It is nevertheless troublesome for the user to turn on or off the power source every time the user moves from one place to another.
In view of the fact that cellular phones adapted to detect their own location as described above are placed into wide use, the present applicant has conceived the idea of specifying an area where no phone calls should be made and causing the phone to automatically reject incoming calls when the location of the phone as detected by GPS or the like is within the specified area. The inventor has also conceived the idea of specifying not only areas but also callers and time as to incoming calls and rejecting the incoming call from the specified person in the specified period of time.
An object of the present invention is to automatically reject incoming calls to a cellular phone as positioned in a specified location at a specified time, and incoming calls from a specified subscriber so as to eliminate the cumbersome procedure of turning on or off the power source.